Remove unused transactional fixtures config

We had `use_transactional_fixtures` enabled but no fixtures where
defined in spec/fixtures. This prevented Capybara tests with javascript
to work. This is explained in detail in
https://github.com/DatabaseCleaner/database_cleaner#rspec-with-capybara-example.

spec/spec_helper.rb

@@ -52,14 +52,6 @@ RSpec.configure do |config|
   # config.mock_with :flexmock
   # config.mock_with :rr
 
-  # Remove this line if you're not using ActiveRecord or ActiveRecord fixtures
-  config.fixture_path = "#{::Rails.root}/spec/fixtures"
-
-  # If you're not using ActiveRecord, or you'd prefer not to run each of your
-  # examples within a transaction, remove the following line or assign false
-  # instead of true.
-  config.use_transactional_fixtures = true
-
   # If true, the base class of anonymous controllers will be inferred
   # automatically. This will be the default behavior in future versions of
   # rspec-rails.
@@ -76,25 +68,51 @@ RSpec.configure do |config|
 
   config.include Features::SessionHelpers, type: :feature
 
-  # Database cleaner configuration
-
-  config.before :suite do
-    DatabaseCleaner.strategy = :transaction
-    DatabaseCleaner.clean_with :truncation
-
-    # Create terms and conditions
+  # Create terms and conditions
+  config.before do
     Document.create(label: "t&c") do |doc|
       doc.title = "Terms and Conditions"
       doc.content = "blah blah blah"
     end
+  end
 
+  # Database cleaner configuration
+  config.before(:suite) do
+    if config.use_transactional_fixtures?
+      raise(<<-MSG)
+        Delete line `config.use_transactional_fixtures = true` from rails_helper.rb
+        (or set it to false) to prevent uncommitted transactions being used in
+        JavaScript-dependent specs.
+
+        During testing, the app-under-test that the browser driver connects to
+        uses a different database connection to the database connection used by
+        the spec. The app's database connection would not be able to access
+        uncommitted transaction data setup over the spec's database connection.
+      MSG
+    end
+
+    DatabaseCleaner.strategy = :transaction
+    DatabaseCleaner.clean_with(:truncation)
+  end
+
+  config.before(:each, type: :feature) do
+    # :rack_test driver's Rack app under test shares database connection
+    # with the specs, so continue to use transaction strategy for speed.
+    driver_shares_db_connection_with_specs = Capybara.current_driver == :rack_test
+
+    if !driver_shares_db_connection_with_specs
+      # Driver is probably for an external browser with an app
+      # under test that does *not* share a database connection with the
+      # specs, so use truncation strategy.
+      DatabaseCleaner.strategy = :truncation
+    end
   end
 
   config.before(:each) do
     DatabaseCleaner.start
   end
 
-  config.after(:each) do
+  config.append_after(:each) do
     DatabaseCleaner.clean
   end